The FBI spent decades tracking mathematician Paul Erdős (2015)

The FBI monitored mathematician Paul Erdős for decades, initially suspecting him of espionage due to his eccentric behavior and connections, particularly with a professor from Communist China. Erdős, a Hungarian mathematician known for his extensive contributions to mathematics and his unique lifestyle, was often seen as a potential threat during the Cold War. His first encounter with authorities occurred in 1941 when he was arrested near a secret radio tower, which he later explained as a misunderstanding related to his mathematical interests. Despite his political critiques of both sides of the Cold War, the FBI ultimately concluded that Erdős posed no real threat, describing him as "purely a mathematician" with a penchant for intellectual freedom. His refusal to take a loyalty oath and his status as a non-diplomatic Hungarian national raised eyebrows, but these were attributed to his academic pursuits. Although he faced visa issues, including being barred from the U.S. in 1954, he was eventually granted a temporary visa with the support of Senator Hubert Humphrey. The FBI's surveillance of Erdős yielded little evidence of wrongdoing, suggesting that their interest was more about his unusual persona than any actual threat he posed.

- The FBI tracked Paul Erdős for decades, suspecting him of espionage.

- Erdős was known for his significant contributions to mathematics and eccentric lifestyle.

- Initial suspicions arose from his connections with a Communist Chinese professor.

- The FBI ultimately found no evidence of wrongdoing, viewing him as a harmless intellectual.

- Erdős faced visa challenges but was supported by political figures like Senator Hubert Humphrey.